Fuel contained in automobile gas tanks presents a source of potential emission of hydrocarbons into the atmosphere. Such emissions from vehicles are termed ‘evaporative emissions’. To prevent evaporative emissions from being discharged into the atmosphere, vehicles may be equipped with evaporative emission control systems (Evap). For example, an Evap system may include a fuel vapor canister coupled to a fuel tank which includes a fuel vapor adsorbent for capturing fuel vapors from the fuel tank while providing ventilation of the fuel tank to the atmosphere. As such, the Evap system may be configured to store refueling vapors, running-loss vapors, and diurnal emissions in the fuel vapor canister, and then purge the stored vapors during subsequent engine operation. The stored vapors may be routed to engine intake for combustion, further improving fuel economy for the vehicle.
In an effort to meet stringent federal emissions regulations, fuel systems and Evap systems may need to be intermittently diagnosed for the presence of undesired vapor emissions that could release fuel vapors to the atmosphere. Undesired evaporative emissions may be identified using engine-off natural vacuum (EONV) during conditions when a vehicle engine is not operating. For example, a fuel system may be isolated at an engine-off event. The pressure in such a fuel system will increase if the tank is heated further (e.g., from hot exhaust or a hot parking surface) as liquid fuel vaporizes, and the pressure rise may be monitored and an undesired amount of vapor emissions may be indicated based on expected pressure rise or expected rates of pressure rise. Furthermore, as a fuel tank cools down, a vacuum is generated therein as fuel vapors condense to liquid fuel. Similarly, vacuum generation may be monitored and an undesired amount of vapor emissions identified based on expected vacuum development or expected rates of vacuum development.
However, the entry conditions and thresholds for a typical EONV test are based on an inferred total amount of heat rejected into the fuel tank during the previous drive cycle. The inferred amount of heat may be based on engine run-time, integrated mass air flow, miles driven, etc. Thus, hybrid electric vehicles, including plug-in hybrid electric vehicles (HEV's or PHEV's), pose a problem for effectively controlling evaporative emissions. For example, primary power in a hybrid vehicle may be provided by the electric motor, resulting in an operating profile in which the engine is run only for short periods. As such, adequate heat rejection to the fuel tank may not be available for EONV diagnostics.
An alternative to relying on inferred sufficient heat rejection for entry into a typical EONV diagnostic test is to instead actively pressurize or evacuate the fuel system and Evap system via an external source. Toward this end, US Patent Application No. 2015/0090006 A1 teaches conducting undesired evaporative emissions detection in an evaporative emission systems control system by using a pump configured to both pressurize and evacuate the system. However, the inventors herein have recognized potential issues with such a method. For example, the use of an external pump introduces additional costs, occupies additional space in the vehicle, and includes the potential for malfunction.
Thus, the inventors herein have developed systems and methods to at least partially address the above issues. In one example, a battery of a hybrid vehicle is inductively charged by coupling a magnetic field between a primary coil external to the vehicle and a secondary coil onboard the vehicle. The magnetic field from the primary coil may be further coupled to a ferrous fuel tank or a ferrous member coupled to the tank. In this way, eddy currents may be induced in the ferrous fuel tank or a ferrous member coupled to the fuel tank, thus generating heat that may actively pressurize the fuel system and Evap system to allow for diagnostic evaporative emissions testing.
In one example, fuel system pressure may be monitored subsequent to vehicle operation with a fuel tank isolation valve (FTIV) closed to seal the fuel tank from atmosphere. If steady pressure or vacuum is not indicated, it may be determined whether inductive charging of the vehicle is in progress. If the vehicle is in the process of inductive charging, the FTIV may be maintained closed such that the fuel system is maintained sealed from atmosphere. In the absence of undesired vapor emissions, pressure may build in the fuel system, resulting from the magnetic field induced heating of the fuel tank. If a pressure rise above a reference pressure is indicated during a portion of the charging, it may be determined that vapor emissions in the fuel system are not undesired. Alternatively, if the pressure does not build to a threshold level, undesired vapor emissions in fuel system may be indicated. If undesired vapor emissions in the fuel system are not indicated, a canister side of the Evap system may subsequently be checked for undesired vapor emissions. As such, the FTIV may be commanded open, the CVV commanded or maintained closed, and pressure monitored for a duration. A pressure maintained above a threshold may indicate that evaporative vapor emissions are not undesired, while a pressure decay below a threshold pressure may indicate the presence of undesired vapor emissions. In this way, both the fuel system and the canister side of the Evap system may be actively checked for undesired vapor emissions during an inductive charging operation without the use of an external pump.
The above advantages and other advantages, and features of the present description will be readily apparent from the following Detailed Description when taken alone or in connection with the accompanying drawings.
It should be understood that the summary above is provided to introduce in simplified form a selection of concepts that are further described in the detailed description. It is not meant to identify key or essential features of the claimed subject matter, the scope of which is defined uniquely by the claims that follow the detailed description. Furthermore, the claimed subject matter is not limited to implementations that solve any disadvantages noted above or in any part of this disclosure.